In general, a capacitance type dynamic quantity sensor device has a sensor chip including a movable electrode which can be displaced in a predetermined direction in accordance with application of a dynamic quantity, and a fixed electrode disposed so as to confront the movable electrode, the movable electrode and the fixed electrode being formed on a substrate such as a semiconductor substrate or the like. The capacitance type dynamic quantity sensor device detects the dynamic quantity on the basis of variation of the capacitance between the movable electrode and the fixed electrode in accordance with application of the quantity amount. The dynamic quantity may be acceleration, angular velocity or the like.
Specifically, a capacitance type dynamic quantity sensor device for detecting a dynamic quantity applied to a surface of a substrate in a horizontal direction is known. This type of sensor is designed so that a fixed electrode of a sensor chip is disposed to confront a movable electrode in a horizontal direction to a surface of a substrate, and the movable electrode is displaced in the horizontal direction. The horizontal direction to the surface of the substrate will be hereinafter referred to as “substrate surface horizontal direction”.
A sensor device including a sensor chip as described above and a circuit chip having a processing circuit for processing a sensor signal from the sensor chip, etc. has been proposed as one of capacitance type dynamic quantity sensor devices for detecting a dynamic quantity in a substrate surface horizontal direction as described above (for example, see JP-A-11-67820).
In the capacitance type dynamic quantity sensor device as described above, one surface of the substrate of the sensor chip and the circuit chip are disposed so as to be face each other, and the sensor chip and the circuit chip are connected to each other through a bump electrode.
Furthermore, there is also known a capacitance type dynamic quantity sensor device which can detect a dynamic quantity in a direction perpendicular to a surface of a substrate in addition to a dynamic quantity in a substrate surface horizontal direction, that is, a capacitance type dynamic quantity sensor device which can detect a dynamic quantity in a multi-axial direction. In the following description, the direction perpendicular to a surface of a substrate will be hereinafter referred to as “substrate surface vertical direction.”
The following problem would occur when a capacitance type dynamic quantity sensor device which can detect a dynamic quantity in a multi-axial direction as described above is constructed.
Here, FIG. 7 is a diagram showing a general construction of the capacitance type dynamic quantity sensor device which can detect the dynamic quantity in the multi-axial direction. Furthermore, FIG. 8A is a plan view showing an example of the specific construction of a horizontal direction detecting unit 900 of FIG. 7, and FIG. 8B is a perspective view showing an example of the specific construction of a vertical direction detecting unit 910 of FIG. 7.
As shown in FIG. 7, the capacitance type dynamic quantity sensor device can be manufactured by using a semiconductor substrate 10 and using well-known semiconductor manufacturing technique and etching technique.
Here, the direction horizontal to the sheet surface of FIG. 7 corresponds to the horizontal direction to a surface of the semiconductor substrate 10 (that is, the substrate surface horizontal direction), and the direction vertical to the sheet surface of FIG. 7 corresponds to the vertical direction to the surface of the semiconductor substrate 10 (that is, the substrate surface vertical direction).
Specifically, FIG. 7 shows a horizontal direction detecting unit 900 having a movable electrode which can be displaced in the substrate surface horizontal direction in accordance with a dynamic quantity such as an acceleration or the like applied in the substrate surface horizontal direction, and a vertical direction detecting unit 910 having a movable electrode which can be displaced in the substrate surface vertical direction in accordance with a dynamic quantity applied in the substrate surface vertical direction.
Wire portions 920 drawn out from the respective detecting units 900 and 910 are formed on the semiconductor substrate 10, and also pads 930 connected to the respective wire portions 920 are formed on the semiconductor substrate 10. These pads 930 will be connected to bonding wires through which the respective detecting units 900 and 910 on the semiconductor substrate 10 are electrically connected to external circuits, etc.
The horizontal direction detecting unit 900 is formed as follows. That is, as shown in FIG. 8A, trench etching is conducted from one surface side of the semiconductor substrate 10 to form grooves, thereby forming a movable electrode 901 and a fixed electrode 902 disposed so as to confront the movable electrode 901 in the substrate surface horizontal direction.
In this case, each of the movable electrode 901 and the fixed electrode 902 is designed to have a comb-shape, and disposed so that the comb-shape teeth thereof are engaged with one another. The movable electrode 901 is joined to the semiconductor substrate 10 through a spring portion (not shown) having a degree of freedom in the substrate surface horizontal direction so as to be displaceable in the substrate surface horizontal direction.
In FIG. 8A, when a dynamic quantity is applied in the substrate surface horizontal direction, the movable electrode 901 is displaced in the same direction, and the distance between the movable electrode 901 and the fixed electrode 902 are varied, so that the capacitance between the movable electrode 901 and the fixed electrode 902 is varied.
This capacitance variation is output as a sensor signal through the wire portions 920, the pads 930 and the bonding wires to an external circuit, thereby detecting the applied dynamic quantity in the substrate surface horizontal direction.
Furthermore, the vertical direction detecting unit 910 is formed as follows. That is, as shown in FIG. 8B, trench etching or sacrifice layer etching and well-known wire forming techniques or the like are conducted from one surface side of the semiconductor substrate 10 to form a movable electrode 911 and fixed electrodes 912 and 913 so that the fixed electrodes 912 and 913 are disposed so as to confront the movable electrode 911 in the substrate surface vertical direction.
Here, the movable electrode 911 is supported by cantilever arms 10a corresponding to the lower side portion of the semiconductor substrate 10, so that the movable electrode 911 is movable in the substrate surface vertical direction.
Furthermore, the fixed electrodes 912 and 913 are formed at the upper and lower sides of the movable electrode 911. The movable electrode 911 and the fixed electrodes 912 and 913 are formed of conductive layers.
In FIG. 8B, when a dynamic quantity is applied in the substrate surface vertical direction, the movable electrode 911 is displaced in the same direction, so that the distance between the movable electrode 911 and the fixed electrode 912 is varied and also the distance between the movable electrode 911 and the fixed electrode 913 is varied. Accordingly, the capacitance between the movable electrode 911 and the fixed electrode 912 and the capacitance between the movable electrode 911 and the fixed electrode 913 are varied. These variations of capacitance are output as a sensor signal corresponding to a differential capacitance variation to the external circuit, thereby detecting the applied dynamic quantity in the substrate surface vertical direction.
As described above, in the conventional capacitance type dynamic quantity sensor device which can detect the dynamic quantity in the multi-axial direction as described above, it is required to equip plural movable and fixed electrodes to detect the two axes (the substrate surface horizontal direction and the substrate surface vertical direction) at the same time. That is, a dedicated detecting unit is equipped for every detection direction of one chip, thereby resulting in an increase of the chip size.
Particularly with respect to the vertical direction detecting unit 910 for detecting the dynamic quantity amount in the substrate surface vertical direction, it is required to fabricate complicated structures by forming the fixed electrodes 912 and 913 as a lower wire and an upper wire as shown in FIG. 8B, resulting in an increase of the manufacturing cost.
Furthermore, in a discrete type dynamic quantity sensor for simultaneously detecting dynamic quantities along two axes (in the substrate surface horizontal direction and the substrate surface vertical direction) on one chip as shown in FIG. 7, many wire portions 920 and pads 930 are needed to carry out wire-bonding between the dynamic quantity sensor and an external circuit.
Accordingly, there is a problem in that the probability of crosstalk between an output from one axis and another axis is increased, that is, the probability that the respective wire portions 920 have electrical influence to one another and noises are superposed on the output is increased.
Furthermore, the arrangement of the wire portions 920 and the pads 930 may become complicated, thereby making wire bonding difficult to perform.
As described above, when a capacitance type dynamic quantity sensor device for detecting a dynamic quantity in a multi-axial direction is implemented, there has hitherto occurred increase of chip size, complication of structures in a wire forming step, a bonding wire forming step, etc.